Stable transduction of quiescent CD34(+)CD38(-) human hematopoietic cells by HIV-1-based lentiviral vectors

We compared the efficiency of transduction by an HIV-1-based lentiviral vec tor to that by a Moloney murine leukemia virus (MLV) retroviral vector, usi ng stringent in vitro assays of primitive, quiescent human hematopoietic pr ogenitor cells, Each construct contained the enhanced green fluorescent pro tein (GFP) as a reporter gene. The lentiviral vector, but not the MLV vecto r, expressed GFP in nondivided CD34(+) cells (45.5% GFP(+)) and in CD34(+)C D38(-) cells in G(0) (12.4% GFP(+)), 48 hr after transduction. However, GFP could also be detected short-term in CD34(+) cells transduced vith a lenti viral vector that contained a mutated integrase gene. The level of stable t ransduction from integrated vector was determined after extended long-term bone marrow culture. Both MLV vectors and lentiviral vectors efficiently tr ansduced cytokine-stimulated CD34(+) cells. The MLV vector did not transduc e more primitive, quiescent CD34(+)CD38(-) cells (n = 8), In contrast, stab le transduction of CD34(+) CD38(-) cells by the lentiviral vector nas seen for over 15 weeks of extended long-term culture (9.2 +/- 5.2%, n = 7). GFP expression in clones from single CD34(+)CD38(-) cells confirmed efficient, stable lentiviral transduction in 29% of early and late-proliferating cells . In the absence of growth th factors during transduction, only the lentivi ral vector was able to transduce CD34(+) and CD34(+)CD38(-) cells (13.5 +/- 2.5%, n = 11 and 12.2 +/- 9.7, n = 4, respectively). The lentiviral vector is clearly superior to the MLV vector for transduction of quiescent, primi tive human hematopoietic progenitor cells and may provide therapeutically u seful levels of gene transfer into human hematopoietic stem cells.